The influence of solvent and sequence on peptide conformation is to be studied, using both cyclic peptides synthesized for the purpose and analogs of luteinizing hormone releasing hormone, LHRH. Sequences that produce conformationallly stable cyclic peptides will be sought for use in designing analogs of biologically active peptides. Solution conformations of the cyclic peptides will be compared with crystal structures where possible. Relationships between solution conformation and biological activity will be sought for the LHRH derivatives. Nuclear magnetic resonance will be the principal spectroscopic tool. Continued development of NMR methods for peptide conformation will be directed to methods for measuring solvent exposure of peptide backbone protons. Cyclic peptides will be used as models from which to obtain qualitative and quantitative measures of interactions between peptide and solvents.